JP2010143077A - Method of manufacturing insert molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a molded article with an insert object completely embedded inside a resin molded article in one molding cycle. <P>SOLUTION: The method of manufacturing the insert molded article comprises the following processes (A)-(C): (A) suction-fixing the insert object 5 to the fixed side cavity surface of a mold having a socket and spigot joint structure, by a vacuum tube 7, (B) closing the mold and filling molten resin into a cavity at pressure (primary holding pressure) lower than mold-opening pressure by an injection molding machine cylinder 3 to fix the insert object 5 to the resin, and (C) injecting the molten resin at the mold-opening pressure or higher after stopping suction of the insert object 5 and completely embedding the insert object 5 inside the resin molded article with the injected resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an insert molded product.

  Insert molded products in which various decorative inserts are insert-molded in resin are used for key holders, mobile straps, fishing equipment, coasters, figurines, wall hangings, and the like. Various methods have been studied as a method for producing such an insert molded product.

For example, an insert for decoration is set in a mold, a resin is filled in the mold, and then cooled and solidified. There is a sandwich molding (Patent Document 2) in which a primary molded product in which a part of the insert is embedded in a resin is made, and then the entire insert is embedded in the resin with a second mold.
JP 2007-223203 A JP 2003-117743 A

  However, when the insert is completely embedded in the resin, the method described in Patent Document 2 requires injection molding of the resin by dividing a plurality of molding cycles, resulting in insufficient productivity.

The gist of the present invention resides in a method for producing an insert-molded product comprising the following steps (A) to (C).
(A) A step of sucking and fixing the insert to the fixed cavity surface of the mold having the wax structure.
(B) A step of closing the mold and filling the cavity with molten resin at a pressure (primary holding pressure) less than the pressure for opening the mold, and fixing the insert to the resin.
(C) A step of injecting molten resin at a pressure higher than the mold opening pressure after stopping the suction of the insert, and completely embedding the insert in the resin molded product by the injected resin.

  According to the manufacturing method of the present invention, a molded product in which an insert is completely embedded in a resin molded product can be manufactured in one molding cycle, and productivity is improved.

  A single molding cycle means that the number of times is one, with the process of “mold closing-injection-holding pressure-cooling / plasticizing-mold opening-removing”, which is an injection molding process, as a molding cycle. It is.

The production method of the present invention comprises the following steps (A) to (C).

(A) A step of sucking and fixing the insert to the fixed cavity surface of the mold having the wax structure. (Figure 1)
In the present invention, the insert 5 is fixed to the fixed cavity surface of the mold 1 having a wax structure by suction.

  The suction port for fixing the insert 5 is installed on the fixed side cavity surface of the mold 1 having a wax structure, and the sintered metal 6 is installed in the suction port so that the resin does not leak.

  The filtration diameter of the sintered metal 6 is preferably 2 μm or more and 20 μm or less, and more preferably 2 μm or more and 15 μm or less so that the injected resin does not leak. The filtration diameter of the sintered metal is the size of the gap between the metal grains, and the material is preferably a metal having corrosion resistance, and more preferably a stainless steel.

  Depending on the shape, size, and rigidity of the insert 5, the suction port installed on the fixed cavity surface of the mold can be enlarged, the number of suction ports can be increased, or the shape of the suction port can be changed. Stabilize the fixing of objects.

  In addition, as a method of sucking and fixing the insert 5, it is preferable to suck by using a vacuum pump.

  The size and shape of the insert are not particularly limited, but it is preferable that the insert has a low resistance to the resin injected into the mold cavity by injection molding, and the fixing by suction on the fixed cavity surface of the mold is stable. Therefore, a shape that is as flat as possible is preferable, and it is more preferable that the insert has higher rigidity. Furthermore, the material of the insert is not particularly limited as long as it does not discolor, decompose, or break depending on the resin to be injection-molded, such as metal, resin, wood, paper, glass, ceramics, and porcelain.

  In addition, the mold having an enamel structure is preferably provided with a hot runner 2. The hot runner 2 is for preventing the gate from being cooled and solidified, and may be a valve type or an open type.

(B) A step of closing the mold and filling the cavity with molten resin at a pressure (primary holding pressure) less than the pressure for opening the mold, and fixing the insert to the resin. (Figure 2)
In the present invention, after the insert 5 is fixed to the fixed cavity surface by suction, the mold is closed, the mold clamping pressure is set to a pressure (primary holding pressure) lower than the pressure for opening the mold, and the molten resin 8 is placed in the cavity. And the insert 5 is fixed to the molten resin 8.

  When the pressure at which the molten resin 8 is filled in the cavity is equal to or higher than the pressure at which the mold is opened, the volume of the cavity increases, and it becomes difficult to embed the insert 5 at a target position in the resin.

  The primary holding pressure is determined by changing the injection pressure in advance and measuring the injection pressure at which the mold opens.

  The resin used for the manufacture of the insert-molded product by injection molding according to the present invention can be either a thermoplastic amorphous resin or a crystalline resin, but the present invention is mainly used for decorative applications. A transparent resin is preferable so that the insert 5 in the resin is visible.

Examples of such resins include polystyrene, acrylonitrile / styrene resin, methacrylic resin, methyl methacrylate / styrene resin, polycarbonate, methyl methacrylate / butadiene / styrene resin, unsaturated polyester resin, polyarylate, and cycloolefin resin.
(C) A step of injecting molten resin at a pressure higher than the mold opening pressure after stopping the suction of the insert, and completely embedding the insert in the resin molded product by the injected resin. (Figure 3)
Next, the cooling process is not performed, and after the suction of the insert 5 is stopped, the molten resin 8 is injected at a pressure higher than the mold opening pressure. By injecting at a pressure higher than the mold opening pressure, the mold can be opened by the resin pressure and the insert 5 can be completely embedded in the resin molded product by the injected molten resin 8.

  The mold opening amount of the mold is set so that the cavity volume becomes the final volume of the target molded product, and is defined by a stopper so as not to open the mold excessively. The stopper is released after completion of the pressure holding process, and is prepared for a mold opening process for taking out a molded product.

Next, the present invention will be described specifically by way of examples. The experiment was performed under the following conditions.

(1) Injection molding machine Toshiba Machine Co., Ltd. IS80FPA3
Screw diameter: φ32mm
Injection pressure: 2030kg / cm ² (gauge pressure 140kg / cm ²⁾
Clamping pressure: 78 tons (gauge pressure 156 kg / cm ² )
(2) Mold (mold having an enamel structure)
Cavity dimensions: 100 mm × 100 mm × 2 mm thickness Hot runner gate: φ3 mm open-type vacuum position: fixed cavity central vacuum suction port: φ10,
Sintered metal for vacuum suction port: stainless steel, filtration diameter 10μm
(3) Vacuum pump: Max-0.1 MPa is used.

(4) mold clamping pressure gauge pressure (Max156kg / cm ²⁾ was set to 40 kg / cm ^2, was set clamping pressure of 20 tonnes.

(Primary holding pressure setting)
The injection pressure and holding pressure under the following molding conditions were increased, and the pressure at which the mold was opened was measured.
Molding condition setting Clamping pressure: Gauge pressure 40kg / cm ² (equivalent to 20 tons)
Injection molding machine cylinder temperature: 270 ° C
Hot runner temperature: manifold 270 ° C, nozzle 270 ° C
Mold temperature: 60 ℃
Injection speed: 20% (Max 99%)
Weighing: 50mm
Screw rotation speed: 35% (70 rpm)
Back pressure: 7%
Molding cycle: Injection time 20 seconds-Cooling time 15 seconds-Intermediate time 2 seconds Total 45 seconds

From the above results, it was confirmed that the mold opening pressure was 63.6 kg / cm ² .

Example 1
A 30 mm × 30 mm × 0.5 mm bamboo plate as an insert was sucked and fixed in the center of a mold having an enamel structure at a vacuum degree of −0.1 MPa of a vacuum pump.

Then closing the mold, a methacrylic resin (Mitsubishi Rayon Co., ACRYPET VH) as a thermoplastic resin and used after drying 16 hours at 80 ° C., the resin with injection pressure 39.6kg / cm 2 ^(primary pressure holding) Ejected.

After holding at the primary holding pressure for 8 seconds, the suction is stopped, the injection pressure is 70.7 kg / cm ² , the mold is opened in the mold opening direction by the resin pressure, and the insert is molded by the injected resin. Fully embedded inside the product.

  The time required for the molding cycle of "mold closing-injection-holding pressure-cooling / plasticizing-mold opening-taking out" is 62 seconds, and the bamboo plate is completely inside the molded product in one molding cycle. An embedded molded product was obtained.

(Example 2)
A molded product was obtained in the same manner as in Example 1 except that the thermoplastic resin was changed to methyl methacrylate / styrene resin (Esthenium MS-600, Nippon Steel Chemical Co., Ltd.) and changed to the following injection conditions.
Injection molding machine cylinder temperature: 250 ° C
Hot runner temperature: manifold 250 ° C, nozzle 250 ° C
Injection pressure: 35.4 kg / cm ² (primary holding pressure)
The time required for the molding cycle of "mold closing-injection-holding pressure-cooling / plasticizing-mold opening-taking out" is 62 seconds, and the bamboo plate is completely inside the molded product in one molding cycle. An embedded molded product was obtained.

(Comparative Example 1)
An insert similar to that in Example 1 was fixed at the center of a mold having an enamel structure at a vacuum degree of −0.1 MPa of a vacuum pump.

  Next, the mold was closed, and a methacrylic resin (Mitsubishi Rayon Co., Ltd. Acrypet VH) as a thermoplastic resin was dried at 80 ° C. for 16 hours. The resin was injected under the same conditions as in Example 1, and the suction was stopped. After cooling, the mold was opened to obtain a primary molded product. The time required for the molding cycle of the primary molded product was 45 seconds.

  Next, with the molded product remaining in the movable cavity of the mold, a metallic spacer having a thickness of 2 mm is placed on the mating surface of the fixed mold and the movable mold to close the mold, and the thickness is within the cavity. A space of 2 mm was created, and the resin was again injected in the same manner as in the above molding conditions to obtain a molded product in which the insert was completely embedded in the resin.

  Although a molded product in which a bamboo plate was completely embedded in the center of the molded product was obtained, the process with a molding cycle of 45 seconds was repeated twice, resulting in insufficient productivity.

The process figure which fixes an insert thing by vacuum suction to the fixed side cavity surface of the metal mold | die which has a wax structure. The process figure which closes a metal mold | die, fills a cavity with resin below the pressure which opens a mold (primary holding pressure), and fixes an insert to resin. After releasing the vacuum suction of the insert, the resin is injected at the primary holding pressure or higher, the mold is opened in the mold opening direction by the resin pressure, and the insert is completely embedded in the resin molded product by the injected resin. Process drawing to do.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold which has wax structure 2 Hot runner 3 Injection molding machine cylinder 4 Injection molding machine screw 5 Insert 6 Sintered metal 7 Vacuum tube 8 Molten resin

Claims (2)

The manufacturing method of the insert molded product which consists of the process of following (A)-(C).
(A) A step of sucking and fixing the insert to the fixed cavity surface of the mold having the wax structure.
(B) A step of closing the mold and filling the cavity with molten resin at a pressure (primary holding pressure) less than the pressure for opening the mold, and fixing the insert to the resin.
(C) A step of injecting molten resin at a pressure higher than the mold opening pressure after stopping the suction of the insert, and completely embedding the insert in the resin molded product by the injected resin.   The method for manufacturing an insert-molded product according to claim 1, wherein the resin to be filled is a transparent thermoplastic resin.

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